The present invention relates to a signal switch network, in particular, a millimeter-wave passive FET (Field Effect Transistor) switch using impedance transformation networks.
High frequency switch is one of the important devices in MMW (millimeter-wave) radio communication system. The performance of a circuit is limited by the devices used in the circuit. As to the high frequency switch used in millimeter-wave band, the isolation, of the switch in on/off state is limited by the FET used in the switch. Since in high frequency, an FET in off state will present low impedance instead of high impedance due to the capacitance between the drain and source of the FET. In addition, high frequency signals between neighbor transmission lines will often couple with one another so as to degrade the performance of the circuit.
Monolithic PIN diode microwave switch has demonstrated excellent performance even up to millimeter-wave frequency. However, since PIN diode cannot be manufactured in MMIC (Monolithic Microwave Integrated Circuit) process of HEMT (High Electron Mobility Transistor, one type of FET), FET switch is still very popular today, because FET can be integrated with other building blocks in a transmit/receive (T/R) module, and presents better linearity than PIN diode. For frequency of 20 GHz or lower, series and/or shunt configurations of an FET with a transmission line can readily serve as a very good switch with excellent isolation and insertion loss. However, for frequency higher than 20 GHz, the parasitic capacitance between the drain and the source of FET will degrade the, isolation performance significantly. Most MMW monolithic FET switches employ indutors to resonate with the parasitic capacitance between the drain and the source of FET, but the isolation of the swich is still lower than 30 dB (please see references [1]xcx9c[4]).
In order to enhance the isolation of the switch, a transmission line with quarter wavelength is used to increase the distance between the switch and the signal line, so as to achieve up to 44 dB isolation (please see reference [5]), but a huge chip area is required, and therefore increase the cost.
Phase cancellation technique, of Lange coupler can also be used to achieve a better isolation performance (please see reference [6]), but several 3 dB and 90xc2x0 Lange couplers are required, and thus increase the layout area.
Recently, compact DCxcx9c60 GHz HJFET MMIC switch was reported with reasonable isolation performance (please see references [7]xcx9c[8]), but a special process/layout for the ohmic electrode sharing technology is required in HEMT devices.
[1] M. J. Schindler and A. Morris, xe2x80x9cDC-40 Gz and 20-40 GHz MMIC SPDT switches,xe2x80x9d IEEE Trans. on Microwave Theory Tech., vol. MTT-35, no. 12, pp. 1486-1493, December 1987.
[2] P. Bermkopf, M. Schindler, and A. Bertrand, xe2x80x9cA high power K/Ka-band monolithic T/R switch,xe2x80x9d in 1991 IEEE Microwave and Millimeter-wave Monolithic Circuits Symposium Digest, pp. 15-8, June 1991.
[3] G. L. Lan, D. L. Dunn, J. C. Chen, C. K. Pao and D.C. Wang. xe2x80x9cA high performance V-Band monolithic FET transmit-receive switch,xe2x80x9d in 1988 IEEE Microwave and Millimeter-wave Monolithic Circuits Symposium Digest, pp. 99-101, June 1988.
[4] M. Aust, H. Wang, R. Carandang, K. Tan, C. H, Chen, T. Trinh, R. Esfandiari and H. C. Yen, xe2x80x9cGaAs monolithic components development for Q-Band phased array application,xe2x80x9d in 1992 IEEE MTT-S International Microwave Symposium Digest, vol. 2, pp.703-706, June 1991.
[5] D. L. Ingram, K. Cha, K. Hubbard, and R. Lai, xe2x80x9cQ-band high isolation GaAs HEMT switches,xe2x80x9d in 1996 IEEE GaAs IC Symp. Dig., Orlando, Fla., pp. 289-282, November 1996.
[6] D.C. W. Lo, H. Wang, Barry R. Allen, G. S. Dow, Kwo Wei Chang, Michael Biedenbender, Richard Lai, Sian Chen, Daniel Yang, xe2x80x9cNovel monolithic multifunctional balanced switching low-noise amplifiers,xe2x80x9d IEEE Trans, on Microwave Theory and Tech., vol. 42, no. 12, pp 2629-2634, November 1998.
[7] H. Mizutani, N. Funabashi, M. Kuzuhara, Y. Takayama, xe2x80x9cCompact DC-60-GHz HJFET MMIC switches using ohmic electrode-sharing technology,xe2x80x9d IEEE Trans. on Microwave Theory and Tech., vol. 46, no. 11, pp. 1597-1603, November 1998.
[8] Kenichi Maruhashi, Hiroshi Mizutani, Keiichi Ohata, xe2x80x9cDesign and performance of a Ka-band monolithic phase shifter utilizing nonresonant FET switches,xe2x80x9d IEEE Trans on Microwave Theory and tech., vol. 48, no. 8, pp. 1313-1317, August 2000.
[9] Yu-Jiu Wang, Kun-You Lin, Dow-Chih Niu, and Huei Wang, xe2x80x9cA V-band MMIC SPDT passive HEMT switch using impedance transformation networks,xe2x80x9d in 2001 IEEE MTT-S International Microwave Symposium Digest., Phoenix, vol. 1, pp. 253-256, May, 2001.
It is therefore an object of the present invention to provide a millimeter-wave passive FET switch using impedance transformation networks, utilizing the standard HEMT manufacturing process to reduce the layout of the chip, and to enhance the performance of the high frequency switch.